1. Field of the Invention
The present invention relates to an outboard engine system wherein a relief valve is provided at an intermediate portion in a cooling water supply passage to supply cooling water from a cooling water pump to a water jacket.
2. Description of the Related Art
In a conventional outboard engine system, cooling water used to cool an engine is taken in through a cooling water intake port provided at a gear case and supplied by a cooling water pump to a water jacket surrounding a combustion chamber. During this process, the pressure of the cooling water supplied to the water jacket is regulated by a relief valve. The outboard engine systems disclosed by Japanese Utility Model Application Laid-Open Nos. 50-127028 and 50-127728 include relief valves wherein a valve body is seated from above into a valve seat, which is disposed in a horizontal direction and protrudes upward.
The relief valve is closed when the engine of the outboard engine system stops and when the engine operates at a low speed. The relief valve opens when the engine operates at a high speed to restrict the upper limit value of the pressure of the cooling water being supplied to the water jacket. When the engine stops, the relief valve closes, the cooling water in the cooling water discharge passage on the downstream side from the relief valve is discharged as is, and the cooling water in the cooling water supply passage on the upstream side reversely flows through a gap in the impeller of the cooling pump that has been stopped and is discharged.
In the relief valve of the above-described conventional outboard engine systems, the valve seat protrudes upward so the valve body is seated from above. Therefore, when the engine stops and the relief valve closes, it has been observed that cooling water stays in a recessed portion surrounding the valve seat.
Further, because particular attention is not paid to the disposition of the cooling water supply passage and the cooling water discharge passage, which are connected to the relief valve, the cooling water simply stays in the vicinity of the relief valve when the outboard engine system is tilted upward to be landed after the engine stops. Likewise, because salt is deposited in the vicinity of the relief valve, the valve body has to be frequently cleaned, resulting in additional and troublesome maintenance work.